Civil Engineering Reference
In-Depth Information
Table 4.28 Maximum Von Mises equivalent stresses and yield margins of safety for basis unit
block module in each on-orbit thermal load case
Design case
r
e
(MPa)
MS
y
Case 1
94.158
0.59
Case 2
125.937
0.19
Case 1 represents the thermal deformation due to on-orbit maximum temperatures
Case 2 represents the thermal deformation due to on-orbit minimum temperatures
Table 4.29 The limiting
angular positioning
deviations for the most
precise equipment relative to
the star sensor
Equipment
Limiting angular positioning
deviations (arcmin)
MBEI (optical-mechanical unit)
30
Angular velocity meters (gyro)
60
Reaction wheels
60
Magnetometer
60
Magnetorquers
60
connecting at least three fixation points. In case of equipment A,
*
1A
and
*
2A
identify its mounting plane before on-orbit thermal deformation.
*
1B
and
*
2B
identify the mounting plane of equipment B. The normal vectors,
*
nA
and
*
nB
to
the mounting planes of equipment A and B, respectively before on-orbit thermal
deformation, can be calculated by applying vector cross product as follows:
*
nA
¼
*
1A
*
2A
*
nB
¼
*
1B
*
2B
The angle between both of these normal vectors is calculated by the formula:
!
*
nA
*
nB
*
nA
h
¼
cos
1
*
nB
After on-orbit thermal deformation, the equipment mounting planes are usually
deformed. Hence, the normal vectors
*
nA
and
*
nB
are modified to
*
0
nA
and
*
0
nB
;
respectively. They are calculated for the deformed mounting planes as follows:
*
0
nA
¼
*
0
1A
*
0
2A
*
0
nB
¼
*
0
1B
*
0
2B
where:
*
0
1A
and
*
0
2A
and
*
0
1B
and
*
0
2B
identify the mounting planes of equipment
A and B, respectively, after on-orbit thermal deformation. These vectors are cal-
culated from the displacement deformation results of on-orbit thermal deformation
analysis in the X, Y, and Z directions.
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